Map from Google - Zimbabwe

Zimbabwe, formerly Rhodesia, is a country located in southern Africa, just north of the Tropic of Capricorn, and almost entirely occupied by a plateau, at an altitude between 4,000 and 5,200 feet, which temper the climate. There are three main seasons: a rainy season, hot and humid from mid-November to mid-March, a cool season, dry and sunny from mid-May to mid-August, and a brief period of intense heat at the end of the dry season, between mid-August and mid-November, before the rains that come during the month of November. The rains lower a bit the temperature, while increasing the relative humidity. Because of this climate with a long dry season, the landscape is savanna, except in the higher mountains where there are forests. The highest peak is Mount Nyangani, 8,504 feet high, located in the east, in the Nyanga National Park.
In much of the country, the annual rainfall ranges from 21.7 to 35.5 inches. The rains occur primarily in the form of showers and thunderstorms in the afternoon. The wettest regions are the north and the east, while the driest region is the south, in the Limpopo Valley on the border with South Africa, where rainfall drops below 16 inches per year. In the latter region, the altitude drops to around 1,600/2,000 feet, while in the south-eastern strip, at the border with Mozambique, where the Gonarezhou National Park is found, it goes down to around 600/1,000 feet. Even in the north there is an area where the altitude drops to around 1,600 feet above sea level, and it's that of Lake Kariba. It goes without saying that the areas where the altitude is lower, are also the hottest, and in October and November highs can reach 105 °F.
Here are the average temperatures of Kariba, near the lake of the same name, at 1,600 feet.
Average temperatures - Kariba
Min (°F)727070665752525766737372
Max (°F)888888888479798491959388

The capital Harare is located in the northeast of the country, at 5,000 feet above sea level, and has a temperate climate: it's pleasantly warm from September to April, with highs around 78/84 °F, even though it becomes a little sticky at the height of the rainy season, ie from December to February. The dry season, from May to August, it's cooler, with highs around 71/75 °F, and lows around 44/48 °F. In the coldest nights, the temperature can approach freezing. The coolest period, however, is also the sunniest. In October and November it can be hot during the day, but not like in the lowlands located below 3,300 feet.
Here are the average temperatures.
Average temperatures - Harare
Min (°F)616159554845454854596161
Max (°F)797979797572727582848279

In Harare, 33 in of rain fall in an average year, of which more than 6 in from December to February, the rainiest period, while it almost never rains from May to September. Here is the average precipitation.
Average precipitation - Harare
Prec. (in)

The famous Victoria Falls are located in the north-west, in the Zambezi river, about 3,300 feet above sea level.
Average temperatures - Victoria Falls
Victoria FallsJanFebMarAprMayJunJulAugSepOctNovDec
Min (°F)646463574843434655636464
Max (°F)868486848177778290919086

Victoria Falls

The Hwange National Park is located in the south-west, it covers nearly 5,800 square miles and is home to large amounts of savannah animals such as lions, elephants and cheetahs.

Sometimes Zimbabwe can be affected by tropical cyclones, which originate in the Indian Ocean, and after passing over Mozambique can reach the eastern regions of the country. Typically they lose strength when penetrating in the mainland, but are still able to bring a good amount of wind and rain. The cyclone season runs from mid-November to May, but they are most likely from late December to mid-April. One more reason to avoid the rainy and sultry season.

When to go

The best time to visit Zimbabwe runs from mid-May to August, having a cooler weather and almost no rains. Of course it can get cold at night, especially above 5,000 feet. Generally in mid-August the temperature begins to rise, and the cold at night becomes rarer. In September and October, the heat can be intense during the day, although at high altitudes the nights remain cool.
The rainiest period, hot and muggy and therefore less desirable, runs from December to February.

What to pack

In winter (June to August): light clothes for the day, as well as sweater, jacket and hat for the evening.
In summer (December to February): light clothes for the day, sun hat; a sweatshirt and a spring jacket for the evening, especially above 3,300 feet; light raincoat or umbrella.